Question

I want to convert my code such that I don’t have to use an extra variable (i.e, s in the example below). I know that there is a way to use iterator but I don’t know how. Can somebody help? Thanks a bunch.

from numbers import Number

a = [[[1,2],[3,4]],[[5,6],[7,8]]]


def trav(root,s):
    if isinstance(root,Number):
        print(str(root) + " -> " + s)
    else:
        s = s + "0"
        trav(root[0],s)
        s = s[:-1]

        s = s + "1"
        trav(root[1],s)
        s = s[:-1]

s = ""
trav(a,s)

Answer 1

Why not just…

def trav(root, s=""):

and then you can omit your s = "" line and call it as trav(a)? Also if you were willing to just inline a thing or two, you could do less slicing:

from numbers import Number

a = [[[1,2],[3,4]],[[5,6],[7,8]]]


def trav(root, s=""):
    if isinstance(root, Number):
        print("%s -> %s" % (root, s))
    else:
        trav(root[0], s + "0")
        trav(root[1], s + "1")

trav(a)

Note that none of this has anything to do with iterators; I’m not sure what you were thinking of there. s here acts as an accumulator argument; perhaps that’s the term you were thinking of?